This invention relates generally to the field of turbochargers and, more particularly, to a turbocharger turbine housing that is specifically designed to reduce thermal stress related cracking due to increased operating exhaust temperatures.
Turbochargers for gasoline and diesel internal combustion engines are devices known in the art that are used for pressurizing or boosting the intake air stream, routed to a combustion chamber of the engine, by using the heat and volumetric flow of exhaust gas exiting the engine. Specifically, the exhaust gas exiting the engine is routed into a turbine housing of a turbocharger in a manner that causes an exhaust gas-driven turbine to spin within the housing. The exhaust gas-driven turbine is mounted onto one end of a shaft that is common to a radial air compressor mounted onto an opposite end of the shaft and housed in a compressor housing. Thus, rotary action of the turbine also causes the air compressor to spin within a compressor housing of the turbocharger that is separate from the exhaust housing. The spinning action of the air compressor causes intake air to enter the compressor housing and be pressurized or boosted a desired amount before it is mixed with fuel and combusted within the engine combustion chamber. The turbine housing and compressor housing are each attached to a common turbocharger center housing that rotatably houses the common shaft extending between the turbine and compressor.
Conventionally, the turbine housing is connected to an engine exhaust manifold via an exhaust inlet flange for receiving the exhaust gas exiting the engine combustion chamber. Exhaust gas directed into the turbine housing enters via the inlet exhaust flange and is directed into one or more passages or volutes in the turbine housing. A volute defines a generally spiral- or circular-shaped passageway through the turbine housing that is designed to direct the exhaust gas radially inward towards the centrally-mounted turbine to spin the turbine.
Turbine housings known in the art can comprise a bifurcated volute arrangement, whereby the volute running through the housing is bifurcated by a partial divider wall. Additionally, turbine housings known in the art comprise a squared-off and nonuniform thickness wall that defines the exhaust inlet flange. It is known that turbochargers comprising such conventional turbine housing designs are prone to develop thermal stresses and thermal stress related cracking. It is believed that such turbine housing thermal stress related cracking is caused, at least in part if not in whole, by the reaction of such conventional design features to the transient thermal loading placed on the turbocharger during normal operation. Such turbine housing thermal cracking results in gas leakage/escape from the turbocharger, which not only reduces turbocharger efficiency but can cause engine problems and engine compartment/ancillary engine component problems associated with the added heat provided to the surrounding environment. The issue of turbine housing cracking is one that is of increasing significance due to current engine operating trends of higher exhaust temperatures driven by retarded fuel timing to reduce NOX emissions and by increased engine ratings.
It is, therefore, desired that a turbocharger be constructed comprising a turbine housing that is designed to minimize and/or eliminate the potential for thermal stress related cracking. It is desired that such turbine housing be retrofittable with existing turbocharger parts to facilitate retrofit application. It is further desired that such turbine housing be configured in such a manner so as to achieve this desired result without adversely affecting other turbocharger performance properties, e.g., turbocharger efficiency.
Turbocharger turbine housings, constructed according to principles of this invention, comprise a generally circular-shaped body having an exhaust gas inlet flange at a radial housing end and an exhaust gas outlet at an axial end. Unlike conventional turbocharger turbine housings, the inlet flange is configured having two openings (thereby forming two volutes through the housing) that are separated by a wall divider, forming an X-shaped pattern. The inlet flange and volutes are additionally configured having rounded and uniform thickness walls with the volute wall adjacent the V-band flange and V-band clamp for attachment to the center housing substantially parallel to the V-band flange and spaced therefrom to preclude a notched configuration.
The volutes are configured having a nonuniform/nonconstant shape and size, and the wall divider is configured having a diminishing area between the volutes, moving through the housing in a direction away from the inlet flange. Moving through the turbine housing away from the exhaust inlet flange, the volutes undergo size and shape changes with respect to one another. Specifically, a first volute undergoes a change in a radial dimension while a second volute undergoes a change in an axial dimension. Moving still further through the housing, the changes in volute shape relative to one another decrease and the wall divider diminishes so that the two volutes are joined together by a common passage, thereby forming a single bifurcated volute.
Configured in this manner, turbocharger turbine housings of this invention operate to minimize thermal stress effects caused from transient thermal loading, thereby minimizing and/or eliminating thermal stress relating cracking to extend turbocharger service life.